MINOR: Remove redundant default parameter values in call to LogSegment.open

[kowshik]

Few call sites in Log.scala were passing redundant default values in their calls to LogSegment.open(...). In this PR, I've cleaned these up. For reference, here is a link to the definition of LogSegment.open:

kafka/core/src/main/scala/kafka/log/LogSegment.scala

Lines 660 to 661 in d252185

	def open(dir: File, baseOffset: Long, config: LogConfig, time: Time, fileAlreadyExists: Boolean = false,
	initFileSize: Int = 0, preallocate: Boolean = false, fileSuffix: String = ""): LogSegment = {

Test plan:
Relying on existing unit and integration tests.

[kowshik]

cc @junrao @ijuma for review

[junrao]

@kowshik : Thanks for the PR. LGTM